This circuit is for traditional old-style telephone lines found in an American 1980s documentation. Components are common and the optical coupler can be replaced with an equivalent.
Found in a 1970s documentation, this circuit has a flat response from 15 Hz to 130 kHz. Modern...
In the figure we have the basic configuration of a timer with the 555, according to Radio Shack's...
This circuit is from an article in the December 1988 issue of Radio Electronics magazine that...